The present invention relates to the detection of weak signals masked by interfering noise. More specifically, but without limitation thereto, the present invention relates to a detector implementing stochastic resonance in multistable detectors to detect and quantify a weak signal in the presence of in-band noise.
Electronic detectors of very weak signals are frequently subject to in-band noise limitations. To detect and quantify signals, for example magnetic flux signals using magnetometers implemented by SQUIDs (superconducting quantum interference devices), elaborate readout/bias schemes coupled with noise-cancellation techniques are typically employed. In practice, however, the effectiveness of these techniques is limited by sensor design constraints.
The detection of periodic signals can, under certain conditions, be aided by the presence of controlled amounts of background noise in the sensor, as long as the sensor is nonlinear; the mechanism for this is known as stochastic resonance. However, one frequently encounters signals having frequencies that make detection difficult. An example of interest is that of signals having extremely high frequencies that cannot be easily detected by conventional electronics, and that might actually fall outside the bandwidth of system noise so that amplification via stochastic resonance or any other noise-mediated technique is impractical.
Superconducting quantum interference devices (SQUIDS) are extremely sensitive detectors of magnetic flux and have been the subject of extensive research and development for over 20 years. Apart from improvements in the basic electronic components used to bias and read the SQUID, few significant improvements have been made in this maturing technology due to the sensitivity of the SQUID to environmental noise. Flux jumps, slew rate and dynamic range are common problems encountered when using SQUIDs in practical applications. A continued need exists for a way to improve SQUID-based detectors beyond their current limitations.